feat(imitation): add article imitation create flow

Introduce 仿写创作: new list and create views, backend imitation service
and prompt templates, worker task routing for imitation jobs, and one-click
rewrite triggers from question citation sources. Surface source article
URL/title on article list/detail, and restrict failed articles to delete-only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/lib/api.ts

@@ -7,6 +7,8 @@ import type {
   ArticleListResponse,
   CreateArticleRequest,
   ArticleVersion,
+  GenerateImitationRequest,
+  GenerateImitationResponse,
   AuthTokens,
   Brand,
   BrandLibrarySummary,
@@ -559,6 +561,12 @@ export const articlesApi = {
   create(payload: CreateArticleRequest = {}) {
     return apiClient.post<ArticleDetail, CreateArticleRequest>("/api/tenant/articles", payload);
   },
+  generateImitation(payload: GenerateImitationRequest) {
+    return apiClient.post<GenerateImitationResponse, GenerateImitationRequest>(
+      "/api/tenant/articles/imitations/generate",
+      payload,
+    );
+  },
   detail(id: number) {
     return apiClient.get<ArticleDetail>(`/api/tenant/articles/${id}`);
   },